Method for determining an alcohol concentration of fuel fed to combustion in a motor vehicle after filling with a fuel of predetermined alcohol concentration

Abstract

In the method for determining the alcohol concentration of the tank fuel after filling up with E85 fuel or E0 fuel, two corridors of possible lambda values for filling with E0 fuel and E85 are established according to the volumes of the tank fuel before and after filling, and the lambda values are taken into account in the evaluation.

1. A method for determining an alcohol concentration of fuel fed to combustion in a motor vehicle after filling a fuel tank of a fuel system with either a first fuel type of a first predetermined alcohol concentration or a second fuel type of a second predetermined alcohol concentration, the method comprising:
 prior to having determined whether the filled fuel type is the first fuel type or the second fuel type:
 establishing a first corridor of possible lambda values associated with filling the tank with the first fuel type, the first corridor being defined between an upper first corridor threshold and a lower first corridor threshold; 
 establishing a second corridor of possible lambda values associated with filling the tank with the second fuel type, the second corridor being defined between an upper second corridor threshold and a lower second corridor threshold; and 
 dynamically adapting at least one of the upper threshold and the lower threshold of each corridor as a function of time and fuel consumption such that an initially large width of at least one of the corridors becomes increasingly smaller; 
 
 determining whether the filled fuel type is the first fuel type or the second fuel type, based on the dynamically adapted first and second corridors, changes to a lambda value measured by a sensor, an alcohol concentration of the fuel tank before filling, and volumes of the fuel tank before and after filling; and 
 in response to determining whether the filled fuel type is the first fuel type or the second fuel type, considering only the corridor corresponding to the determined filled fuel, and ignoring the other corridor, for a subsequent evaluation of measured lambda values. 
 
     
     
       2. The method according to  claim 1 , further comprising identifying an error in the fuel system when measured lambda values do not lie in at least one of the first and second corridors. 
     
     
       3. The method according to  claim 1 , further comprising diagnosing, using measured lambda values as input variables, when the measured lambda values lie within at least one of the first and second corridors. 
     
     
       4. The method according to  claim 1 , further comprising establishing and taking into account certain changes to lambda values during the determining as a result of components in the fuel system ageing. 
     
     
       5. The method according to  claim 4 , wherein the establishing and taking into account certain changes to lambda values includes allowing specific changes to the lambda values according to
   Δ Lam =Δ BT +Δ A  
 
 for an operating point before and an operating point after the filling, where Δ Lam  is a difference between a measured lambda value and a lambda value for fuel of an alcohol concentration of 0% and Δ BT  and Δ A  are ageing and alcohol-specific proportions of the difference. 
 
     
     
       6. The method according to  claim 4 , wherein determined ageing-specific changes to the lambda values are taken into account when determining the thresholds of the first and second corridors. 
     
     
       7. The method according to  claim 1 , wherein the first fuel type is a fuel of an alcohol concentration of 85% and the second fuel type is a fuel of an alcohol concentration of 0%. 
     
     
       8. A method for determining an alcohol concentration of fuel fed to combustion in a motor vehicle, comprising:
 filling a fuel tank of a fuel system with either a first fuel type of a first alcohol concentration or a second fuel type of a second alcohol concentration; 
 without knowledge of whether the filled fuel type is the first fuel type or the second fuel type:
 establishing a first corridor of possible lambda values associated with filling the tank with the first fuel type, the first corridor being defined between an upper first corridor threshold and a lower first corridor threshold; 
 establishing a second corridor of possible lambda values associated with filling the tank with the second fuel type, the second corridor being defined between an upper second corridor threshold and a lower second corridor threshold; 
 measuring changes to a lambda value by a lambda sensor after the filling; and 
 dynamically adapting at least one of the upper threshold and the lower threshold of each corridor as a function of time and fuel consumption such that an initially large width of at least one of the corridors becomes increasingly smaller; 
 
 evaluating the filled fuel based on the dynamically adapted first and second corridors, the measured changes to the lambda value, an alcohol concentration of the fuel tank before the filling, and volumes of the fuel tank before and after the filling. 
 
     
     
       9. The method according to  claim 8 , wherein only one of the first and second corridors is taken into account during an evaluation of lambda values, once the filled fuel type is identified. 
     
     
       10. The method according to  claim 8 , further comprising identifying an error in the fuel system when measured lambda values do not lie in at least one of the first and second corridors. 
     
     
       11. The method according to  claim 8 , further comprising diagnosing, using measured lambda values as input variables, when the measured lambda values lie within at least one of the first and second corridors. 
     
     
       12. The method according to  claim 8 , further comprising establishing and taking into account certain changes to lambda values during the evaluating as a result of components in the fuel system ageing. 
     
     
       13. The method according to  claim 12 , wherein the establishing and taking into account certain changes to lambda values includes allowing specific changes to the lambda values according to
   Δ Lam =Δ BT +Δ A  
 
 for an operating point before and an operating point after the filling, where Δ Lam  is a difference between a measured lambda value and a lambda value for fuel of an alcohol concentration of 0% and Δ BT  and Δ A  are ageing and alcohol-specific proportions of the difference. 
 
     
     
       14. The method according to  claim 12 , wherein determined ageing-specific changes to the lambda values are taken into account when determining the thresholds of the first and second corridors. 
     
     
       15. The method according to  claim 8 , wherein the first fuel type is a fuel of an alcohol concentration of 85% and the second fuel type is a fuel of an alcohol concentration of 0%.